Flow Profiling recipes

 Flow profiling in espresso involves controlling the rate at which water flows through the coffee puck during brewing to influence extraction and flavor. Recipes often involve a pre-infusion phase with a low flow rate, followed by a gradual increase and then a decrease in flow to optimize the extraction and compensate for changes in the coffee puck's resistance.

 

In understanding Flow Profiling we need to understand Flow Rate:

This is the speed at which water passes through the coffee bed, measured in milliliters per second (ml/s) or grams per second (g/s). 

Water debit is a term used frequently.

This is the speed that water exits the shower screen (when nothing is inhibiting it).

That is there is no puck, portafilter, etc.

This typically falls within the range of 200-250ml per 30 seconds. (6.66g/s - 8.33g/s)

My ECM Classika is fitted with a Flow Control knob.

Stock, these E-61 machines have a flow of about 7g/s.

To get  similar flow (with the flow control) turn 1.25 revolutions from the fully closed position.

0.25 revolutions = 2g/s

0.50 revolutions =  4g/s

0.75 revolutions = 5.5g/s

1.00 revolutions = 6.25g/s

1.25 revolutions  = 7.0g/s

1.5  revolutions   = 7.7g/s

1.75  revolutions = 8.3g/s

2      revolutions  = 10g/s 

These measurements are specific to my machine. It will of course change if I tweak the OPV.

This range is often cited as a "sweet spot" or a range that is most forgiving for achieving a good espresso extraction. 

To measure this place a glass under the shower screen and measure the amount being collected every second. (its easier if you measure the amount of H20 after 30 secs & divide by 30).

Most machines have a water debit between 4g/s  to 10g/s.

It's commonly 5g/s for vibratory pump machines & 8g/s for those with rotary pumps.

It's important to distinguish between water debit (flow rate without a portafilter) and flow rate during espresso extraction (which is influenced by the portafilter and coffee puck). 

The pic on the left is from my Gagguino. 

Adaptive mode.

The flow starts at zero, quickly rises to 8.5

then drops to zero. Then rises to 4 and drops 

to 1- 0.5

In Flow Profiling we adjust the flow rate throughout the shot to influence extraction and compensate for changes in the coffee bed. 

Flow & pressure are linked.

Pressure = Flow x Resistance

Modern espresso machines, particularly those with flow control and pressure profiling, allow for adjustments to water debit, enabling finer control over the extraction process. 

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Common Flow Profiling Techniques:

Ramping Pre-Infusion:

Starting with a low flow rate to saturate the grounds evenly, then gradually increase the flow rate to build pressure. 

Tapering Flow at the End:

Reducing the flow rate towards the end of the shot to maintain a consistent output and prevent over-extraction. 

Compensating for Grind Changes:

Adjusting the flow rate on-the-fly to compensate for changes in grind size or freshness of the coffee.

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General Recipe:

Start with a flow rate that allows for full saturation (e.g., 7-8 ml/s), then reduce the flow to soak the puck (e.g., close the valve to return to 2 bar), and then adjust the flow rate to reach the desired pressure and extraction. 

Benefits of Flow Profiling:

Improved Extraction: Helps to extract more evenly and consistently from the coffee puck. 

Reduced Channeling: Ramping pre-infusion helps mitigate or eliminate channeling, leading to more even extraction. 

Flavor Control: Allows for greater control over the final flavor profile of the espresso by influencing the extraction of different compounds. 

Compensating for Grind Size: Adjusting flow can compensate for minor grind size variations. 

Tips for Using Flow Profiling:

Start with small adjustments:

Begin by making small changes to the flow rate and observe the impact on the shot. 

Use visual cues:

Pay attention to the appearance of the espresso stream and the pressure gauge to guide your adjustments. 

Experiment with different profiles:

Try different flow rates and timings to find what works best for your coffee and your taste preferences. 

Consider your machine:

Different machines have different capabilities and characteristics, so adapt your approach accordingly. 

Coffee Group-heads

 The group head, also known as the brew head, is the part of an espresso machine where water from the boiler is dispensed into the coffee filter basket. 

Espresso machines utilize different types of group heads, which are essential components responsible for delivering pressurized water to the coffee grounds in the portafilter for extraction. The design of the group head can affect factors such as temperature stability, water distribution, and espresso flavor.

It serves as a meeting point, connecting the machine to the group handle and the hot water to the coffee grounds.

I think that the he most significant difference between different group head designs is how they are heated. 

The group head essentially consists of two main components: the portafilter and the water distribution system.

Most commonly, group heads come in 8-hole (single), 12-hole (double), and 20-hole (triple) configurations. 

In all group heads you will find a gasket & a shower-screen.

The gasket is a thick rubber band that creates a seal between the portafilter and the group-head.

The shower-screen distributes or showers water evenly over the puck.

(As an aside, cleaning your gasket & shower screen regularly is impt)

There are many types of group heads. Technology is constantly evolving

and its difficult to keep up with new improvements.

It is not that straightforward to classify them into simple categories. Some may share the same name but with a slightly different mechanism, while some have different designs but works the same.

The main types of group heads that you will come across are :

Conventional.

Saturated.

semi-saturated

E61.

Lever.

Electrically (electronically) heated

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Conventional.

Also known as traditional or commercial group heads, these are the most common type of espresso machines. They are simple in design making them straightforward in brewing espresso

and giving you a sleek no frills look. 

The inner pipes are housed inside, so the external casing isn't hot to the touch.

They use 3 way solenoid valves to reduce excess pressure after brewing.

These group heads are not heated so aren't the most thermally stable when compares to E-61 or saturated groups.

Standard group heads typically have a large, circular design with a central dispersion screen or shower screen. While it may not be the best group head for thermal stability, 

it is a proven tech with simple construction, and is cheaper to produce and maintain than other more complex group heads.

Examples are  Rocket Boxer, Nuova Simonelli Musica/Osca, and Rancilio Silvia V6.

Saturated

These group-heads are connected to the boiler itself.

The water circulates continuously around the group head from the boiler.

The entire group head is thus heated, ensuring that the brewing water remains at a consistent temperature throughout the extraction process. 

This results in improved temperature stability because the group is saturated with the same body of water whose temperature is being controlled in the boiler. 

These types of groupheads usually heat up much faster that E-61 groups.

Synesso and La Marzocco both use saturated groups. Obviously, a saturated group can only work with machines that have separate steam and brew boilers.

Note that this water in the saturated group head is not used to brew. It just circulates.

Saturated group heads are often found in higher-end espresso machines and are favored by specialty coffee enthusiasts.

Left is a "ring style" saturated group head.

examples:  La Marzocco GS, GS2, GS3 (GS = Group Saturated) machines.  GB5, Linea Classic, La Marzocca GS3 or Slayer, Synesso, Rocket R Nine One, Wendougee Data S, Arkel Coast and Kees van der Westen.

The La Marzocca "goosehead" style is found on many of their machines like the GS3.

Some cheaper machines like the Gaggia Classic pro employ a similar idea. The Gaggia's boiler is right above the group-head. So heating the boiler will heat up everything (including the group-head).

• GS - all about Saturated groups

Semi-saturated

The group head is separated from the boiler by a heat exchange mechanism that directs water flow around the group head.

 A semi-saturated group head features a separate water path from the boiler to the group head, which allows for precise temperature control and consistency. .....maybe the temps are a little less stable than a saturated head.

Lever

There are two sub-categories within this type: spring piston and manual piston. With a manual piston group head, the user has direct control over the water flow through the coffee grounds to brew the espresso. On the other hand, a spring piston group head uses a lever to compress a spring, creating pressure to force water through the coffee grounds. Both of these types offer varying degrees of control to the barista and may impact the espresso quality.

Examples; Pro 800 by Profitec and Leva by La Marzocco ,  Robot Barista by Cafelat 

E61

Named after the Faema E61 espresso machine.

The Faema got its name from a solar eclipse that occurred in 1961.

It's a design that is very tried and true and is one that is used on many prosumer grade espresso machines and even some commercial machines like the Faema Legend and the Faema Jubile.

This design uses a thermosyphon heating system where heated water circulates between the boiler and the group head to maintain a stable temperature. 

It's basically a radiator. Hot water leaves the top section of the boiler and enters the top of the e-61 group head (the mushroom). It begins to cool.... then travels back to the bottom of the boiler.

There is no pump running. The thermosyphon is a passive heat management system.

That big chunk of metal radiates water around the machine to impart thermal stability.

These are easy to spot as the portafilter sits outside the machine and is connected to a brew lever that operates it. Lots of people love these as they look great and do a decent job.

Plus, it is a very simple and reliable design. For example, it incorporates a mechanical 3-way valve with no need for a separate solenoid.

 This design helps to prevent temperature fluctuations during brewing and ensures consistent extraction. Thermosyphon group heads are commonly found in high-quality commercial espresso machines.

The E61 became a group head template for manufacturers, each making slight variations on the design to suit their own requirements leading to the introduction of multiple boilers to their machines.

It takes about 25 minutes or longer to heat up an E61.

The Rocket Apartamento is an iconic E61 machine, followed by ECM Classika, Profitec Pro 400, and Lelit Bianca.

Electronically heated.

The group head is electrically heated with heating elements that are inside the group-head itself. These elements are usually controlled by a thermostat, or PID. Since the heating elements are embedded in the group head they are very efficient in maintaining thermal stability.

You often see these in entry level machines (though not always).

The Bezzera BZ-10 has a electronically heated e-61 style group head. Other examples are the Profitec Go & Move, Rocket Bicocca and the Stone espresso.

 They are very fast at reaching brewing temperatures

Fellow Espresso Series 1

features a commercial-style, heated group head designed for high thermal stability.

The group head has a brass core, a dedicated heating element, and a 90-second heat-up time to mimic the stability of a saturated group.

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